Massive shedding of polymorphonuclear leukocytes (PMN's) into tracheobronchial secretions characterizes exacerbations of bronchitis in human subjects and may damage airway epithelial cells. Chemotaxis, migration to chemical attractants, of PMN's has been demonstrated in vitro across filters. In vivo complement independent chemotaxis of PMN's into hamster airways in response to extracts of cotton trash and the E. coli bacteria or culture supernatant now provides a reproducible model system to analyze morphological events in the passage of PMN's from the blood-vascular system through submucosa and epithelial barriers into airway lumens. Repeated leukocyte migration through the epithelium may damage it resulting in chronic disease. In the series of studies outlined in this protocol, in vivo events associated with leukocyte recruitment will be reproduced and studied utilizing high resolution electron microscopy coupled with freeze-fracture or etch techniques. Permeability changes associated with the inflammatory responses will be evaluated using the electron dense stains lanthanum and horseradish peroxidase as macromolecular markers. Selected histochemical techniques will be adopted to study leukocyte lysosomes, vacuolizaton and surface structure as related to the migration response. Pharmacological agents which may modify leukocytes or their migration will be studied in the model system. Finally, bronchial biopsies from patients with various clinical diseases will be analyzed by microscopy to determine the extent to which these reflect PMN leukocyte migration and epithelial alterations as modelled in hamsters.